feat: add FFT-based audio spectrum analyzer module

- Implement radix-2 Cooley-Tukey FFT algorithm
- Add windowing functions: Hann, Hamming, Blackman, Rectangular
- Support configurable frequency bin count
- Add peak detection with configurable decay rate
- Include temporal smoothing for visualization
- Add spectrum analysis example program
- Proper memory management with init/close lifecycle

Bug-fix: Add buffer bounds checking to prevent overflow when sample count is not power of 2
Signed-off-by: Srikanth Patchava <spatchava@meta.com>

src/raudio_analyzer.h

@@ -0,0 +1,95 @@
+/**********************************************************************************************
+*
+*   raudio_analyzer - Audio spectrum analysis module for raylib
+*
+*   DESCRIPTION:
+*       FFT-based audio spectrum analysis with windowing functions, peak detection,
+*       and smoothing for real-time audio visualization.
+*
+*   FEATURES:
+*       - Radix-2 Cooley-Tukey FFT algorithm
+*       - Multiple windowing functions (Hann, Hamming, Blackman, Rectangular)
+*       - Configurable frequency bin count
+*       - Peak detection with configurable decay rate
+*       - Temporal smoothing for stable visualization
+*
+*   LICENSE: zlib/libpng
+*
+*   Copyright (c) 2024 raylib contributors
+*
+*   This software is provided "as-is", without any express or implied warranty. In no event
+*   will the authors be held liable for any damages arising from the use of this software.
+*
+*   Permission is granted to anyone to use this software for any purpose, including commercial
+*   applications, and to alter it and redistribute it freely, subject to the following restrictions:
+*
+*     1. The origin of this software must not be misrepresented; you must not claim that you
+*     wrote the original software. If you use this software in a product, an acknowledgment
+*     in the product documentation would be appreciated but is not required.
+*
+*     2. Altered source versions must be plainly marked as such, and must not be misrepresented
+*     as being the original software.
+*
+*     3. This notice may not be removed or altered from any source distribution.
+*
+**********************************************************************************************/
+
+#ifndef RAUDIO_ANALYZER_H
+#define RAUDIO_ANALYZER_H
+
+#include <stdbool.h>
+
+//----------------------------------------------------------------------------------
+// Defines and Macros
+//----------------------------------------------------------------------------------
+#ifndef MAX_SPECTRUM_BINS
+    #define MAX_SPECTRUM_BINS       1024
+#endif
+#ifndef DEFAULT_SMOOTHING_FACTOR
+    #define DEFAULT_SMOOTHING_FACTOR  0.8f
+#endif
+#ifndef DEFAULT_PEAK_DECAY_RATE
+    #define DEFAULT_PEAK_DECAY_RATE   0.95f
+#endif
+
+//----------------------------------------------------------------------------------
+// Types and Structures Definition
+//----------------------------------------------------------------------------------
+
+// Window function types for FFT preprocessing
+typedef enum {
+    WINDOW_RECTANGULAR = 0,     // No windowing (rectangular/boxcar)
+    WINDOW_HANN,                // Hann (raised cosine) window
+    WINDOW_HAMMING,             // Hamming window
+    WINDOW_BLACKMAN             // Blackman window
+} WindowFunction;
+
+// Spectrum analyzer configuration
+typedef struct {
+    int binCount;               // Number of frequency bins (must be power of 2)
+    WindowFunction windowFunc;  // Window function to apply before FFT
+    float smoothingFactor;      // Temporal smoothing factor [0.0 - 1.0]
+    float peakDecayRate;        // Peak value decay rate per frame [0.0 - 1.0]
+    int sampleRate;             // Audio sample rate in Hz
+} SpectrumConfig;
+
+//----------------------------------------------------------------------------------
+// Module Functions Declaration
+//----------------------------------------------------------------------------------
+
+// Lifecycle management
+void InitSpectrumAnalyzer(SpectrumConfig config);   // Initialize spectrum analyzer with config
+void CloseSpectrumAnalyzer(void);                   // Free all allocated resources
+
+// Spectrum processing
+void UpdateSpectrum(float *samples, int sampleCount);   // Process audio samples through FFT
+void ApplySmoothing(void);                              // Apply temporal smoothing to spectrum data
+
+// Data retrieval
+float *GetSpectrumData(void);       // Get array of frequency bin magnitudes
+float GetPeakFrequency(void);       // Get the dominant frequency in Hz
+float GetPeakMagnitude(void);       // Get the magnitude of the peak frequency bin
+int GetSpectrumBinCount(void);      // Get the current number of frequency bins
+bool IsSpectrumReady(void);         // Check if analyzer is initialized and ready
+
+#endif // RAUDIO_ANALYZER_H